1. Field of the Invention
The present invention relates to a styrene-based resin composition and process for producing molding products thereof, more specifically it relates to a styrene-based resin composition which comprises a styrene-based polymer having a high degree of syndiotactic configuration and specific components mixed therewith, and a process for producing molding products prepared from the composition, which has a high crystallinity, an excellent surface gloss property and an excellent mold-releasing property.
2. Description of the Related Arts
A styrene based polymer produced by the radical polymerization method, etc. has an atactic configuration in stereostructure. It is molded into various shapes by various molding methods such as injection molding, extrusion molding, blow molding, vacuum forming and flow-in molding, for example, and is widely used for electric domestic appliances, office equipments, domestic appliances, packaging, toys, furnitures, synthetic papers and other industrial materials. However, the styrene-based polymer having an atactic configuration has drawbacks of insufficient mechanical strength, heat resistance and chemical resistance since it is not crystallized.
The group of the present inventors have succeeded to develop a styrene-based polymer having a high degree of syndiotacticity, and also developed a composition in which other components are blended with the styrene-based polymer (Japanese Patent Application Laid-Open Nos. 104818/1987, 257948/1987 and 257950/1987). This styrene-based polymer having a high degree of syndiotactic configuration or a composition thereof has excellent mechanical strength, heat resistance, solvent resistance and electric characteristic as compared with a styrene-based polymer having an atactic configuration and its composition. However, the molding product obtained by using the styrene-based polymer having a high degree of syndiotacticity as a raw material requires high molding temperature to crystallize.
In Japanese Patent Application Laid-Open No. 201350/1989, there is proposed to accelerate the crystallization of a styrene-based polymer having a syndiotactic configuration by blending a specific nucleating agent, and the mold-releasing property and appearance of the molding products therefrom have been improved.
According to this technique, while physical properties or appearance of the composition or the molding products obtained can be improved, there remains some problems that crystallization rate is insufficiently high and surface gloss of the molding products is poor.